I would like to get the confirmation whether this scenario valid or not. please, see the below.
site A, B, C, D is using BGP AS # 64555 and each site is peered with BGP AS # 12345. these site does not need to peer with IBGP session. each site is totally separated as physically. but, those site is advertising different subnets each other.
This scenario assumes all of site A, B, C, D is under MPLS VPN. if so, if ISP( AS # 12345) use BGP AS override, then would it be work? the customer doesn't want to use different AS # due to their management overhead like so.
Please, kindly let me know if there are identical environment or, it works or not.
Yes, the service provider has to use as-override [or similar knob] to send routes learned from one site to the other. It should work fine.